Electric circuit interrupter



March 22, 1949. c. H. HoDGKlNs ELECTRIC CIRCUIT INTERRUPTER Filed Jan.8, 1943 rml? sa-451.1211; 90 I.

ze fr Patented Mar. 22, 1949 auazso ELECTRIC cmcurr IN'rEaaUP'rEacharles n. magma, Fairfield, conn., assigner to The Bryant ElectricCompany,

Bridgeport,

Conn., a corporation of Connecticut Application January 8, 1943, SerialNo. 471,688

35 claims. (ci. 20o-122) This invention relates in general to electriccircuit interrupters, and more specifically to circuit breakers of thetype employing a snap-acting bimetal element as part of the contactactuating means, and to heating means for bimetal elements.

One object oi this invention is to provide a circuit breaker of the typehaving a snap-acting bimetal element for actuating the breaker contacts,with novel means for supporting and actuating the bimetal.

Another object of this invention is to lprovide a novel circuit breakerconstruction capable oi' introducing a double-break in the circuit.

Another object of this invention is to provide novel supporting andactuating means for a snapacting bimetal element oi' the type havingthree legs connected at opposite ends.

Another object of this invention is to provide a circuit breaker of thetype employing a snap acting bimetal element to actuate the breakercontacts, with novel actuating means for the element which is trip-free.

Another object of this invention is to provide novel heating means for abimetal element.

A further object of this invention is to provide a novel circuit breakerconstruction using a snapacting bimetal element, which is relativelysimple inv form yet eillcient in operation.

These and other objects oi' this invention will become more apparentupon consideration of the following detailed description of preferredembodiments thereof, when taken in connection with the attached drawing,in which:

Figure 1 is a longitudinal section view of a circuit breaker embodyingthis invention with the bimetal element and contacts show n inelevation;

Fig. 2 isa transverse section of the breaker shown in Fig. 1 takensubstantially on the line II-II thereof; l

Fig. 3 is a view like Fig'. 1 with the breaker shown in the open circuitposition;

Fig. 4 is a plan view of the bimetal element used in the breaker shownin Figs. 1 to 3;

Fig. 51s an enlarged section of one contact and a portion of thebimetal;

Fig. 6 is a plan viewoi' a thermal relay using a heater similar to thatshown in Figs. 1 to 4;

Fig. 7 is a side elevation view in Fig. 6; and

Fig. 8 is an enlarged cross-'section of the support and heater for thebimetal element shown in Figs. 6 and 7.

The invention is shown as being embodied in a circuit breaker adapted tobe mounted within a. casing 2, preferably of a molded insulatingmaterial. Casing 2'includes opposite end walls I and opposed side walls8, all integrally joined with a bottom wall 6. A cover l0 may beprovided for the open side of the casing, and the cover may be removablysecured in position, for example, as by screws i2. Terminal strips I4are secured in recesses provided in bottom wall 6 of the casing adjacentopposite ends thereof by eyelets I8. Eyelets I8 are preferablyinternally threaded for receiving terminal screws I8 for securingelectrical conductors thereto to connect the breaker in an electriccircuit. Each terminal plate I4 also has secured thereon a contactelementg20 which may be of any good electrical conducting andarcresistant material. w

A bimetal element `22 is employed, and this is constructed in thewell-known manner of a pair of laminations of materials having differentcoeillcients of thermal expansion, respectively. Thus, bimetal element22 has the lamination 2i thereof of a material which has a lowercoeil'cient of thermal expansion than the lamination 23. Theselaminations are secured together in any desired manner, such, forexample, as by welding or the like. The bimetal element is provided witha pair of `spacedlongitudinally extending slots 25 (Fig. 4) terminatingshort of the ends of the element to form a middle leg 24 and a pair ofoutside legs 26. The side legs 26 are deformed. as shown at 28, toshorten the outside legs and thereby place the middle leg under`compression and cause it to assume a bowed form, as shown in Figs. 1 and3.

oi' the relay shown A bimetal element formed like the element 22 iscapable of movement with a snap action upon reversal of curvature ofmiddle leg 24. 'I'his reversal of curvature of middle leg 24 may beaocomplished mechanically to cause reversal of curvature to take placein opposite directions, or it may take place in the upward direction, asviewed in Fig. 1, by the application of heat to the bimetal elementcausing more rapid expansion of lamination 23 than of lamination 2|.Thus bimetal element 22 is capable of automatically moving with a snapaction from the position shown in Fig. 1 to that shown in Fig. 3, whenitis heated a predetermined amount.

Bimetal element 22 is supported on a supporting screw 30 which isthreaded into a thimble I2 rotatably mounted in bottom wall 6 of thebreaker casing. As shown, a wear-resistant washer 34 may be providedbetween the enlarged outer head of thimble 32 and bottom wall 6. Theouter enlarged head of thimble 32 is slotted as shown, so that it may berotated to vary the amount supporting screw 3D is extended into thecasing. The inner end of supporting screw 30 is provided with anenlarged head 36 flared upwardly towards a reduced extension 38. Theextension 38 is adapted to pass through an aperture 31 providedsubstantially centrally of middle leg 24 of the bimetal element, and ahead member 40 is secured to extension 38 and it, in turn, is flaredtowards the bimetal element. Head member 40 is provided with a slot 42in the upper portion thereof for a purpose to be described.

The bimetal element 22 is provided with a contact structure 44 at eachend therof for cooperation with the fixed contacts 20. Each contactstructure 44 includes a block 46 of resistance material, preferably anon-metallic resistance material such as carborundum, carbon, or thelike. Resistor block 46, when entirely or ,part of nonmetallicresistance material, is preferably provided with thin layers of metal48, such, for example, as copper or the like, sprayed or otherwisedeposited upon opposite surfaces of the block to facilitate assemblythereof. A contact element 50 is secured tol one surface of the resistorblock having a metallic layer 48-for example, as by soldering, brazingor the like. A metal conducting plate 52 is secured to the oppositesurface of the resistor block in the same manner, and this, in turn, issecured to bimetal element 22 by soldering, brazing, riveting or thelike. With a contact con- I struction of this type, it will be notedthat the resistor element is sandwiched between contact element 50 andbimetal element 22, and mechanically as well as electrically joins theseelements. This forms a relatively simple yet ecient manner forassociating a resistor element of this type with a bimetal element, andit will also be noted that the resistor elements are placed at thepoints of concentration of current ow in good heat ccnducting relationwith respect to the bimetal element. This is of special importance forbreakers having low current ratings where it is necessary to supplyauxiliary means for heating the bimetal element other than thatgenerated by current flow through the element itself.

In order to actuate bimental element 22, an

. actuating yoke 54 has the mid-portion thereof received in slot 42 ofsupporting screw head member 40, and the legs 56 thereof slidablysupported in grooves 51 cut in opposite side walls 8 of the casing. Theopposed inner edges of the yoke legs 56 have notches 58 cut therein forreceiving the outer legs 26 of bimetal element 22. An actuating handle60, preferably constructed of a molded insulating material, is providedwith an enlarged base portion positioned at least in part in an apertureprovided in casing cover plate i0. The enlarged base 6I of the handle ishollowed out, as shown at 62, for receiving a metal actuator 63, aportion of which is embedded Within handle 60 and extends into hollowedportion 62 at one side thereof, and is provided with an integral ,4 tactuating projection 64 extending across the opening of hollowed portion62 of the handle. Actuating projection 64 is adapted to extend throughan aperture 66 provided in an integral extension of actuating yoke 54.Handle 6l is adapted to be pivotally mounted in the breaker casing by apivot pin 68 passing through the handle and through actuator 63 to havethe opposite ends thereof rotatably mounted in bearings 18. Thesebearings 1l are preferably mounted in slots cut in opposite side walls 8of the casing, and are held in place by cover il.

It will now be apparent that movement of 'handle 60 about its pivot 68will cause sliding of actuating yoke 54 toward and away from bimetalelement 22. It will be noted that slots 58 in the legs of actuating yoke54 are of considerably greater extent than the thickness of bimetalelement 22, so that there is considerable lost motion between theactuating yoke and the outer legs 26 of the bimetal element. There isalso lost motion between handle 60 andyoke 54 because of the loose fitof projection 64 in aperture 66. It will be noted that the lost motionis positive in character in both instances because flexing of thebimetal element by handle 60 is intimately caused by positive mechanicalengagement of the parts. The purpose of providing this lost motion is sothat in actuating the bimetal element, snap action thereof may takeplace independently of the handlefor example, assuming it is desired tomove the breaker from closed-circuit position shown in Fig. l to theopen-circuit position shown in Fig. 3--handle 60 should be moved in, acounterclockwise direction. During the first part of this motion, thebimetal element is not moved, and is not even engaged until the bottomof yoke slots 58 engage the undersides of the outer legs 26 of thebimetal element. As soon as this occurs, the outer legs 26 of thebimetal element are raised relative to the point of support for middleleg 24. Middle leg 24 being bowed and under compression acts similar toa toggle, so that when the outer legs are raised the middle leg will, atan overcenter position, suddenly reverse its curvature with a snapaction, and cause the bimetal element to assume the position shown inFig. 3, wherein the ends thereof are moved upwardly to separate contactstructures 44 from fixed contacts 20. The lost motion between handle 60and the bimetal element is arranged so that this snap movement of thebimetal element may take place irrespective of the rate of movement ofhandle 6U merely by taking up the lost motion between the handle andouter legs 26 of the bimetal element. When it is desired to close thecircuit, handle 60 is merely rotated in a clockwise direction from theposition shown in Fig. 3 towards the position shown in Fig. l. This willcause downward movement of yoke 54 until thev upper ends of slots 58engage outer legs 26 of the bimetal element, whereupon these outer legswill be moved downwardly until the point is reached where middle leg 24of the bimetal element will suddenly reverse its curvature and causeclosing of the breaker contacts with a snap action. This also occursindependently of the rate of movement of handle 60 by taking up the lostmotion between the handle and the outer legs of the bimetal element.

In order to maintain the handle 60 at olf and on" positions, anovercenter spring arrangement is provided comprising a coil tensionspring 12 anchored at one end in an anchor plate 14.

and the plate itself isreceived in grooves cut in opposite sidewalls lof the casing, and is maintained; in position by cover plate Il. Theother end of spring 12 is hooked over a spring yoke 1I, the arms ofwhich extend on opposite sides oi' the enlarged portion Il of thehandle, and are hooked, as at 14, to engage in depressions formed onenlargements 19 provided at each side of handle 6l.

As shown in Fig. 1, handle 66 is maintained in the position shown.because the line of action oi' spring 12 is above handle pivot 69. andthe handle cannot move'any further in a clockwise direction because ofthe engagement of the ends of yoke legs 66 with the ends of grooves 61.Assuming that the handle is movedin a counterclockwise direction fromthe position shown in Fig. 1, the bimetal element will be caused to openthe circuit with a snap action as described above, and as soon as thehooked ends 16 of spring yoke 1l pass below handle pivot 68, the handlewill be biased in a counterclockwise direction so that when theoperating force is removed it will be moved to the position shown inFig. 3 and maintained in this position. As stated before, in moving theswitch handle to openthe circuit, bimetal element 22 is moved by thehandle only an amount suiiicient to causey reversal of curvature ofmiddle leg 24, whereupon the contacts separate independently of movementof the handle. Consequently, the handle may move in a counterclockwise`direction beyond the snapping point of bimetal element 22 by virtue ofthe lost motion between the handle and the outer legs 26 of the bimetalelement. The snapping point of bimetal element 22 is correlated with theovercenter point of spring 12, so that if the handle is released at thetime when bimetal element 22 snaps to open circuit position, spring 12will then have moved overcenter to cause handle 60 to be moved to theposition shown in Fig. 3. Substantially the same action takes place inmanually closing the breaker. During the first part of clockwisemovement o! handle 60 vfrom the position shown in Fig. 3, lost motionbetween the handle and legs 26 of the bimetal element is taken up whilespring 12 is stressed, and iinaliy legs 26 of the bimetal element arelowered by yoke 54 to cause snap-acting closure of the breaker contacts.At the same time spring 12 passes overcenter to restore handle 66 to theposition shown in Fig. l. The parts are arranged so that upon anautomatic opening of the circuit, due to an overload suillcient to causeheating of bimetal element 22, either by itself or by heat conductedfrom resistor blocks 46, an amount sufficient to cause the bimetal toautomatically reverse its curvature, handle 60 will be moved to itsnormal oil position shown in Fig. 3. Because of thelost motion betweenactuating yoke 64 and the outer legs of the bi-` metal element,automatic opening of the circuit may occur even though actuating handle60 is held in its normal closed circuit position, shown in Fig. 1.However, such an automatic operation of the bimetal element will causeengagement of the upper ends of slots 68 in actuating yoke 64 by theouter legs 26 of the bimetal element, and these will exert some upwardpressure on the yoke. Enough pressure in an upward direction will beexerted by legs 26 of the bimetal element when in the position shown inFig. 3 to move handle 60, when it is not held in the Fig. 1 position, anamount suillcient to move spring 'I2 over- .bimetal element.

6 center and thereby throw the handle to the positionshowninll'ig. 3.Thusitcanbeseenthat the handle will be moved to its normal oi!" positionin response to an automatic opening of the breaker contacts. y

lIn Pigs. 6, 7 and 8, there is illustrated a diilerent manner oi'assembling heating means and a The bimetal element in this case is shownas embodied in a thermal relay mounted on an insulating plate l0. Afpair of terminal strips 42 and I4 are secured to the base 99 at spacedpoints in any desired manner, such, for example, as by eyelets Il.' Abimetal strip 46 is adapted to be supported on the terminal strip 92 andcomprises a pair of laminations 41, I9 intimately joined together as,for example, by welding or the like. In this instance, the lamina-l tion99 should be of a material having a higher coeiiicient of thermalexpansion than the lamination 91. A non-metallic resistor block 66similar to block 46 is provided with a relatively thin metallic coating96 on opposite faces thereof, like the coating 4I on block 46 previouslydescribed. These coated faces of resistor block Il may then be solderedor brazed to bimetal eleyment 86 and terminal strip 92, respectively, torigidly mechanicallyrmount. the bimetal strip at one end of the terminalstrip 92. The other end.

of bimetal strip 86 is provided with a contact element 92 thereon forengagement with a cooperating contact 94 provided on terminal strip 44Since current in flowing between terminal strips 82 and I4 must passthrough resistor block 99, it'is obvious that currents above apredetermined value will cause heating of resistor block 86 and thiswill be conducted to the bimetal element and raise the temperaturethereof. As the temperature of the bimetal strip rises, it will distortto move contact 92 out of engagement with contact 94 and thereby openthe circuit therebetween.

The particular relay disclosed is also provided with a shunt resistorwire 96 connecting terminal strips 92 and 94, so that "when contacts 92and 94 are separated, resistor 96 will supply heat to bimetal strip 86and maintain the contacts separated so long as currents above apredetermined value flow in the circuit.

In the foregoing applicant has disclosed a' circuit breaker constructionutilizing a snap-acting bimetal element which may be manually actuatedto open and close the breaker contacts with a snap action, and yet whichis capable of movement with a snap action both when manually actuatedand automatically actuated in response to predetermined heating thereof,independently of the'rate of movement of the operating handle. Thebreaker contacts will also be opened with a snap action in response topredetermined heating of the bimetal element, even if the actuat-l inghandle is held at its closed position. There has also been disclosed anovel arrangement for supporting and actuating a snap-acting bimetalelement, as well as novel means for associating an auxiliary heater withbimetal elements in general. The` circuit breaker constructiondisclosed,

-statutes, it is desired that the invention be not limited to theseparticular structures, because it will be obvious'particularly topersons skilled in the art that many modiilcations and changes may bemade therein without departing from the broad spirit and scope of thisinvention. Accordingly, it is desired that the invention be interpretedas broadly as possible, and that it be limited only as required by theprior art.

I claim as my invention:

1. In a circuit breaker, separable contacts. a flexible snap-actingbimetal element for automatically separating said contacts in responseto predetermined conditions,'manually operable means movable in oppositedirections to open and close said contacts, said manually operable meansflexing said element upon movement in said opposite directions to movesaid element at least to its snapping point, and a positive lost motionconnection between said manually operable means and element permittingthe snap action of said element to take place independently of themovement of said manually operable means.

2. In a circuit breaker, separable contacts, a flexible snap-actingbimetal element for automatically separating said contacts in responseto predetermined conditions, manually operable means movable in oppositedirections to open and close said contacts, said manually operable meansflexing said element upon movement in said opposite directions to movesaid element at least to its snapping point, a positive lost motionconnection; between said manually operable means and element permittingthe snap action of said element to take place independently of themovement of said manually operable means, and means for moving saidmanually operable means to extreme positions upon movement thereof insaid opposite directions, respectively, to at least partly take up saidlost motion.

3. In a circuit breaker, separable contacts, a

flexible snap-acting bimetal element for automatically separating saidcontacts in response to predetermined conditions, manually operablemeans movable in opposite directions to open and close said contacts,said manually operable means flexing said element upon movement in saidopposite directions to move said element at least to its snapping point,a positive lost motion connection between said manually operable meansand element permitting the snap action of said element to take placeindependently of the movement of said manually operable means, and anovercenter spring for biasing said manually operable means to spacedpositions upon movement thereof in said opposite directions,respectively, to at leastl partly take up said lost motion.

4. In a circuit breaker, separable contacts, a flexible snap-actingbimetal element for automatically separating said contacts in responseto' predetermined conditions, manually operable means movable in onedirection to close said'contacts, said manually operable means ilexingsaid element upon movement in said one direction to move said element atleast to its snapping point,

and a positive lost motion connection between said manually operablemeans and element permitting snap movement of said element to close thecontacts independently of movement of said manually operable means. .l

5. In a circuit breaker, separable contacts, a flexible snap-actingbimetal element for automatically separating said contacts in responseto predetermined, conditions, manually operable means movable in onedirection toclose said contacts, said means flexing said element uponmovement in said one direction tn move said element at least to itssnapping point, a positive lost motion connection between said manuallyoperable means and element permitting snap movement of said element toclose the contacts independently of movement of said manually operablemeans, and means responsive to movement of said manually operable meansin said one direction an amount suiiicient to cause snap action closingmovement of said element, for biasing said manually operable means formovement a further amount to take up at least a part of said lostmotion.

6. In a circuit breaker, separable contacts, a flexible snap-actingbimetal element for automatically separating said contacts in responseto predetermined conditions, manually operable means movable in onedirection to close said contacts, said means tlexing said element uponmovement in said one direction to move said elementat least to itssnapping point, a positive lost motion connection between said manuallyoperable means and element permitting snap movement of said element toclose the contacts independently of movement of said manually operablemeans, an overcenter spring responsive to movement of said manuallyoperable means in said one direction an amount suillcient to cause snapaction closing movement oi said element, for biasing said manuallyoperable means for movement a further amount to take up at least a partof said lost motion, and said element operative upon automatic operationthereof to move said manually operable means an amount at least suicientto move said spring overcenter so that said manually operable means willbe moved in an opposite direction to a position indicating such anautomatic operation and wherein it is operable to reclose the breaker.

7. In a circuit breaker, separable contacts, a flexible snap-actingbimetal element for opening and closing said contacts with a snapaction, said element being responsive to predetermined heating thereofto automatically open said contacts, a movable actuating handle, meansactuated by said handle having spaced operating parts positioned toengage said element when said handle is moved in opposite directions,respectively, to iiex said element to cause snap action opening andclosing of said contacts, respectively, whereby snap action of saidelement occurs in the space between said parts independently of the rateof movement of said handle.

8. In a circuit breaker, separable contacts, a flexible snap-actingbimetal element for opening and closing said contacts with a snapaction, said element being responsive to predetermined heating thereofto automatically open said contacts, an actuating handle adapted whenmoved in opposite directions to flex said element to cause snap actionopening and closing of said contacts, respectively, means whereby snapaction of said element occurs independently of the rate of movement ofsaid handle, and means responsive to automatic operation of said elementto move said handle to one extreme position independently of saidelement. V

9. In a circuit breaker, separable contacts, a flexible snap-actingbimetal element for opening and closing said contacts with a snapaction, said element being responsive to predetermined heating thereofto automatically open said con- Q tacts,an actuating handle adapted whenmoved in opposite directions to flex said element to cause snap actionopening and closing of said contacts, respectively, said handle havingpositive lost motion with said element whereby snap action of saidelement occurs independently of said handle, and means effective to biassaid handle to an extreme positionv in each direction in response tomovement of said handle in each direction an amount sufilcient to causesnap action of said element.

10. In a circuit breaker, separable contacts, a flexiblesnap-actingbimetal element for opening andclosing said contacts with a snap action,said element being responsive to predetermined heating thereof toautomatically open said contacts, an actuating handle adapted whenmovedin opposite directions to `flex said element to cause snap actionopening and closing Aof said contacts, respectively, vsaid handle havingpositive lostmotion with said element whereby snap action of saidelement occurs independently of said handle, means eifective to bias-said handle to an extreme lposltion in each direction in response tomovement of said Ahandle -in each di-` rection an amount sumcient tocause snap action of said element, and said element effective, upon anautomatic operation thereof, to -move said handle toward the extremeposition it normally occupies when said contacts Iare open an amountsumcient to render said biasing means effective tact means carried by atleast said one end of.

l said'element for movement into and out of ento move said handle theremainder of the distance.

11. In a circuit breaker, a flexible snap-acting bimetal element havinga plurality of substantially parallel legs connected at opposite ends,supporting means secured to an intermediate portion of one oi' saidlegs, manuallyoperable actuating means engageable with another of saidlegs to move it laterally relative to said one leg, at least one end ofsaid element being free to move laterally, relatively stationary contactmeans,

contact means carried .by at least'said one end of said element formovement into and out of en- I gagement with said relatively stationarycontact means, and said element being initially deformed so thatmovement of said actuating means in opposite directions will causesnap-acting movement of said movablecontact` means into and out ofengagement with said relatively stationary contact means. l

12. In a circuit breaker, a flexible snap-acting bimetal element,supporting means secured to an intermediate portion of said element at apoint spaced from the, edges thereof, manually operable actuating meansengageable with an intermediate portion of said element at a pointspaced from said supported portion to move said second mentioned portionlaterallyrelative to said supportedportion, at least one end of saidelement being free to move laterally, relatively stationary contactmeans, contact means carried byat .leastf said one end of said elementfor movementfinto and out of engagement with said relativelylstationarycontact means, and said elementA being initially deformed so thatmovement of said actuating means in opposite directions will causesnap-acting movement of said movable contact means into and out ofengagement with said relatively stationary contact means.

13. In a circuit breaker, a flexible snap-acting bimetalelement havingthree substantially parallel legs connected at their oppos-ite ends,said element being stressed so that at least one leg assumes a bowedform, supporting means segagement with said relatively stationarycontact means whereby movement of said actuating means in oppositedirections will cause snap action movement of said movable contact meansinto and out of engagement with said relatively stationaryY contactmeans. v

14. In a circuit breaker, a ilexible-snap-acting bimetal element havingthree substantially parallel legs connected at their opposite ends, saidelement being stressed so that the middle leg assumes a bowed form,supporting means secured to an intermediate portion of said bowed leg,manually operable actuating means includ- -ing a yokehaving endsengageable with the other legs to move said other legs laterally inopposite directions to cause reversal of curvature of said bowed leg, atleast one end of said element being free to move laterally, relativelystationary contact means, contact means carried by at least said one endof said element for movement into and out of engagement with saidrelatively stationary contact means, whereby movement of said actuatingmeans in opposite directions will cause snap action movement of saidmovable contact means into and out of engagement with said relativelystationary contact means.

15.l In a circuit breaker, a flexible snap-acting bimetal Aelementhaving three substantially parallel legs connected at their oppositeends, said element being stressed so that the middle leg assumes a bowedform, supporting means secured to an intermediate portion of said bowedleg, manually operable actuating means including a yoke slidably mountedfor movement laterally toward and away from said element, said yokehaving ends engageable with the other legs to move said other legslaterally in opposite directions to cause reversal of curvature of saidbowed leg, at least one end of said element being free to movelaterally, relatively stationary contact means, contact means carried byat least said one end of said element for movement into and out ofengagement with said relatively stationary contact means, wherebymovement of said actuating means in opposite directions will cause snapaction movement of said movable contact means into and out of engagementwith said relatively stationary contactk means. x

16. In a circuit breaker, a exible snap-acting bimetal element having aplurality of substantially parallel legs connected at opposite ends,supporting means secured to an intermediate portion of one of said legs,manually operable vactuating means engageable with another of saidcontact means including a contact element secured on a block ofresistance material by good electrical and heat conducting means.

17. In a circuit breaker, a flexible snap-acting bimetal element havinga plurality of substantially parallel legs connected at opposite ends,supporting means secured to an intermediate portion of one of said legs,manually operable actuating means engageable with another of said legsto move it laterally relative to said one leg, opposite ends of saidelement being free to move laterally, spaced relatively stationarycontact means, contact means carried by each end of said element formovement into and out of engagement with said relatively stationarycontact means, and said element being initially deformed so thatmovement of said actuating means in opposite directions will causesnap-acting movement of said movable contact means into and out ofengagement with said relatively Lstationary contact means.

18. In a circuit breaker, a exible bimetal element, supporting means forsaid element, stationary contact means, contact means on said elementmovable therewith into and out of engagement with said stationarycontact means, and at least one of said contact means including acontact element secured on a block of resistance material by goodelectrical and heat conducting means.

19. A bimetal element, heating means therefor comprising a block ofresistance material, and means of a good electrical and 'heat conductingmaterial interposed between said element and block and being rigidlybonded to both and in intimate contact therewith for securing said blockto said element.

20. A bimetal element, heating means therefor comprising a block ofnon-metallic resistance material, and means of a good electrical andheat conducting material interposed between said element and block andbeing rigidly bonded to both and in intimate contact therewith forsecuring said block to said element,

21. A bimetal element, heating means therefor comprising a block ofnon-metallic resistance material, a metallic coating on one face of saidblock, and means of a good electrical and heating conducting materialinterposed between said element and block for securing said coated faceof the block to said element.

22. A bimetal element, a terminal therefor, a block of resistancematerial interposed between said element and terminal, and separatemeans interposed between said block and element and between said blockand terminal withl each of said means being rigidly bonded to themembers adjacent its opposite sides and in intimate engagement therewithfor mechanically securing said block to said element and terminal withopposite faces of said block in good electrical and heating conductingrelation with said element, and at least in good electrical conductingrelation with said terminal, respectively.

23. A bimetal element, a contact element therefor, a block of resistancematerial interposed between said element and contact element, and meansfor mechanically securing said block between said element and contactelement with opposite faces of said block in good electrical and heatconducting relation with said element, and at least in good electricalconducting relation with said contact element, respectively.

24. A bimetal element, a terminal therefor, a block of non-metallicresistance material interposed between said element and terminal, ametallic coating on opposite faces of said block, and means of a goodelectrical and heat conducting material interposed between said blockand element and between said block and terminal for securing saidopposite'faces of the block to said element and terminal, respectively.

25. A bimetal element, a contact element therefor, a block ofnon-metallic resistance material interposed between said elements, ametallic vcoating on opposite faces of said block, and means of a goodelectrical and heat conducting material securing said opposite faces ofthe block to said element and contact element, respectively.

26. A bimetal element, an electrical conductor, a block of non-metallicresistance material interposed between said element and electricalconductor, a metallic coating on opposite faces of said block and meansof a good electrical and heat conducting/ material interposed betweensaid block and element and between said block and terminal for securingsaid opposite faces of the block to said element and electricalconductor, respectively.

27. In a circuit breaker, separable contacts, a. flexible snap-actingbimetal element for opening and closing said contacts lwith a snapaction, said element being responsive to predetermined heating thereofto automatically open said contacts, an actuating handle adapted whenmoved in opposite directions to flex said element to cause snap action.opening and closing of said contacts, respectively, and trip-freeoperating means connecting said handle and said element so that saidelement is capable of opening said contacts in response to saidpredetermined heating thereof even when said handle is held in aposition corresponding to the closed position of said contacts.

28. In a circuit breaker, separable contacts, a flexible snap-actingbimetal element for opening and closing said contacts with a snapaction, said element being responsive to predetermined heating thereofto automatically open said contacts, an actuating handle adapted whenmoved in opposite directions to flex said element to cause snap actionopening and closing of said contacts, respectively, said handle beingtrip-free of said element so that said element is capable of openingsaid contacts in response to said predetermined heating thereof evenwhen said handle is held in a position corresponding to the closedposition of said contacts, and means responsive to an automatic circuitopening operation by said element to move said handle to a positioncorresponding to the open position of said contacts when lsaid handle isnot held at its closed contact position.

29. In a circuit breaker, a flexible snap-acting bimetal element havingatleast a pair of substantially parallel legs connected at theiropposite ends, said element being stressed so that at least one of saidlegs assumes a bowed form, supporting means secured to one of said legs'and manually operable actuating means engageable with the other of saidlegs to move said other leg laterally in opposite directions to causereversal of curvature of said bowed leg, the one of said meansassociated with said bowed leg being located intermediate the endsthereof, at least one end of said element being free to movelaterally,relatively stationary contact means, contact means carried by at leastsaid one end of said element for move-A ment into and out of engagementwith said relatively stationary contact means whereby movel 13 ment cisaid actuating means in opposite directions will cause snap actionmovement oi said `movable \contact means into and out o! engagesaidelement, one oi said means adapted to engage said element 'at a pointintermediate the extent of said curvature, the other of said meansadapted to engage said element at a spaced point so that operation ofsaid actuating means in opposite directions will cause relative movementof said spaced points of said element to cause corresponding reversaloi' curvature of said element, relatively stationary contact means, andcontact means on a movable portion oi said element adapted to move intoand out of engagement with said stationary contact means in response toreversal of curvature of said element.

31. In a circuit breaker, a flexible snap-acting bimetal elementhavingatleast a portion thereof curved in section so as to be operable inresponse to predetermined Ltemperature change to automatically reversethe curvature of said portion with a snap-action, supporting means forsaid element, manually operable actuating means for said element, saidsupporting means being secured to said element at a point intermediatethe extent of said curvature, said actuating means adapted to engagesaid element at a spaced point, so that operation of said actuatingmeans in opposite directions will cause relative movement of said spacedpoints of said element to cause corresponding reversal oi' curvature ofrsaid element, relatively stationary contact means, and contact means ona movable portion of said element adapted to move into and out ofengagement with said stationary contact means in response to reversal ofcurvature of said element.

32. In a circuit breaker, a ilexible snap-acting bimetal element havingat least a portion thereof curved in section so as to be operable inresponse to predetermined temperature change to automatically reversethe curvature of said portion with a snap-action, supporting means forsaid element, manually operable actuating means for said element, one ofsaid means adapted to engage said element at a point intermediate theextent of said curvature, the other of said means adapted to engage saidelement'at a spaced point so that operation of said actuating means inopposite directions will cause relative movement of said spaced pointsof said element to-cause corre.

spending reversal of curvature of said element, relatively stationarycontact means, said actuating means having lost motion relative to saidelement so that snap-action movement of said element may occur at apredetermined rapid rate independent of the rate of movement of saidactuating means, and contact means on a movable portion of said elementadapted to move into and out of engagement with said stationary contactmeans in response to reversal of curvature of said element.

33. In a circuit breaker, a flexible snap-acting bimetal element havingat least a portion thereof curved in section so as to be operable inresponse to predetermined temperature change to automatically reversethe curvature oi said portion witha snap-action, supporting means forsaid element, manually operable actuating means ior said element, one ofsaid means adapted to engage said element at a point intermediate theextent oi said curvature, the other oi' said means adapted to engagesaid element ata spaced point so that operation of said actuating meansin opposite directions will cause relative movement of said spacedpoints of said element to cause corresponding reversal of curvature oi'said element, relatively stationary contact means, said actuating meanshaving lost motion relativeto said element yso that snap-action movementof said element may occur at a predetermined rapid rate independent ofthe rate oi' movement of said actuating means, means biasing said handleto take up at least a' portion of said lost motion so that the positionof said actuating means clearly indicates the operation last performed,and contact means on a movable portion of said element adapted to moveinto -and out of engagement with said stationary contact means inresponse to reversal oi. curvature of said element.

34. In a circuit breaker. a flexible snap-acting bimetal element havingat least a portion thereof curved in section so as to be operable inresponse to predetermined temperature change to automatically reversethe curvature of said portion with a snap-action, supporting means forsaid element, manually operable actuating means for said element, one ofsaid means adapted to engage said element at a point intermediate theextent of said curvature, the other of said means adapted to engage saidelement at a spaced point so that operation of said actuating means inopposite directions will cause relative movement oi said spaced pointsof said element to cause corresponding reversal of curvature of saidelement, relatively stationary contact means, said actuating meanshaving lost motion relative to said element so that snap-action movementof said element may occur at a predetermined rapid rate independent ofthe rate of movement of said actuating-means, means biasing said handleto take up at least a portion of said lost motion so that the positionof said actuating means clearly indicates the operation last performed,stop means for preventing movement of said actuating means under theinfluence of said biasing means from taking up all of said lost motionso that said element may automatically reverse its curvature even thoughsaid actuating means is held at an extreme position, and contact meanson a movable portion of said element adapted to move into and out ofengagement with said stationary contact means in response to reversal ofcurvature of said element.

35. In a circuit breaker, a iiexible snap-acting bimetal element havingat least a portion thereof curved in section so as to be operable inresponse to predetermined temperature change to automatically reversethe curvature of said portion with a snap-action, supporting means forsaid element, manually operable actuating means for said element, one ofsaid means adapted to engage said element at a point intermediate theextent of said curvature, the other. of `said means adapted to engagesaid element at a spaced point so that operation of said actuating meansin opposite directions will cause relative movement of said spacedpoints of said element to cause corresponding reversal of curvature of'said element. relatively stationary contact means, said actuating meanshaving lost motion relative to said element so that snap-action`movement of 15 said element may occur at a predetermined rapid rateindependent of the rate of movement of said actuating means, meansresponsive to movement of said actuating means an amount sufiicient tocause snap-action movement of said element for biasing said handle totake up at least a portion of said lost motion so that the position ofsaid actuating means clearly indicates the operation last performed,said' biasing means also being responsive to automatic operation of saidelement to bias said actuating means to a position indicating such anoperation of the element, and contact means on a movable portion of saidelement adapted to move into and out of engagement with said stationarycontact means in response to reversal of curvature of said element.

CHARLES H. HODGKINS.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 851,420 Hewitt et al Apr. 23,1907 1,181,742 Coolidge May 2, 1916 1,898,174 Dubilier Feb. 21, 19332,255,330 ,Platz Sept. 9, 1941 2,257,793 Frank Oct. 7, 1941 2,262,397Immel et al Nov. 11, 1941 2,268,229 Walle Dec. 30, 1941 2,285,450McCarthy June 9, 1942 2,293,179 Swingle Aug. 18, 1942 2,295,456 EatonSept. 8, 1942 2,345,451 Bolesky Mar. 28, 1944

